{
  "bibcode": "2021GCN.29925....1G",
  "body": "J.D. Gropp (PSU), J. A. Kennea (PSU), A. Y. Lien (GSFC/UMBC),\nF. E. Marshall (NASA/GSFC), K. L. Page (U Leicester),\nD. M. Palmer (LANL), B. Sbarufatti (PSU), M. H. Siegel (PSU) and\nA. Tohuvavohu (U Toronto) report on behalf of the Neil Gehrels Swift\nObservatory Team:\n\nAt 17:39:33 UT, the Swift Burst Alert Telescope (BAT) triggered and\nlocated MAXI J1803-298 (trigger=1046414). Swift slewed immediately to the source. \nThe BAT on-board calculated location is \nRA, Dec 270.742, -29.818 which is \n   RA(J2000) = 18h 02m 58s\n   Dec(J2000) = -29d 49' 05\"\nwith an uncertainty of 3 arcmin (radius, 90% containment, including \nsystematic uncertainty).  As is usual with an image trigger, \nthe available BAT light curve shows no significant structure. \n\nThe XRT began observing the field at 17:46:59.5 UT, 446.4 seconds after\nthe BAT trigger. XRT found a bright X-ray source located\nat RA, Dec 270.7590, -29.8302 which is equivalent to:\n   RA(J2000)  = 18h 03m 2.16s\n   Dec(J2000) = -29d 49' 48.7\"\nwith an uncertainty of 5.9 arcseconds (radius, 90% containment). This\nlocation is 68 arcseconds from the BAT onboard position, within the BAT\nerror circle and consistent with being MAXI J1803-298. No event data are \nyet available to determine the column density using X-ray spectroscopy. \n\nThe initial flux in the 2.5 s image was 7.51e-10 erg cm^-2 s^-1 (0.2-10\nkeV). \n\nUVOT took a finding chart exposure of 150 seconds with the White filter\nstarting 454 seconds after the BAT trigger. There is a candidate counterpart in\nthe rapidly available 2.7'x2.7' sub-image at\n  RA(J2000)  =\t18:03:02.79 = 270.76162\n  DEC(J2000) = -29:49:49.7  = -29.83046\nwith a 90%-confidence error radius of about 0.61 arc sec. This position is 8.2\narc sec. from the center of the XRT error circle. The estimated magnitude is\n15.82 with a 1-sigma error of about  0.14. No correction has been made for the\nlarge, but uncertain, extinction expected.",
  "circularId": 29925,
  "createdOn": 1619978746000,
  "email": "amy.y.lien@nasa.gov",
  "subject": "Swift Detection of MAXI J1803-298 including an optical counterpart",
  "submitter": "Amy Lien at GSFC  <amy.y.lien@nasa.gov>"
}